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8/11/2019 ATM Basic v1
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1 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Basics
8/11/2019 ATM Basic v1
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2 Nokia Siemens Networks Presentation / Author / Date
For internal use
Synchronous Transfer Mode
Derived from TDM technology
Divides the physical bandwidth into logicaltimeslots
Circuit switched networks (voice and leased lines)
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3 Nokia Siemens Networks Presentation / Author / Date
For internal use
Asynchronous Transfer Mode
A compromise for voice, data, and video
QoS defined/negotiated when the initial connection ismade
Asynchronous on layer 2 of the OSI reference model
Compromise of STM and PTM
Voice Video Data
ATM cells
48-octet
Payload
ATM 53-octet cells are
switched in hardware
8/11/2019 ATM Basic v1
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4 Nokia Siemens Networks Presentation / Author / Date
For internal use
New world packet networks
Layer 1 to layer 3 in the OSI reference model
Layer 1: PDH or (Plesiochronous Digital Hierarch)
SDH/SONET (Synchronous Digital Hierarchy)(Synchronous Optical Network, SONET)
DWDM optical(Dense Wave Division Multiplexing)
Layer 2:
ATM
Frame Relay
PPP (Point to Point Protocol)
EthernetLayer 3:
IP (Internet Protocol)
8/11/2019 ATM Basic v1
5/595 Nokia Siemens Networks Presentation / Author / Date
For internal use
What is ATM & Why
ATM = Asynchronous Transfer Mode
Fast packet switching and multiplexing technology (cell-based )
ATM provides efficient supportfor transmission ofvoice, data, and video
ATM provides QoS guaranteeand reliability
ATM utilises statistical multiplexing, so
less bandwidth can be reserved
transmission cost saving are considerable
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For internal use
For a group of bursty connections,less bandwidth can be reserved thanif bandwidth reservation would bebased on the peak rate of theconnections
Most of the traffic sources sendbursty traffic and with a highprobability all the sources do notsimultaneously transmit at their peakrate
One of the proposed advantages ofATM is that statistical multiplexinggain can be utilized
Statistical multiplexing gain
Statistical multiplexing Deterministic multiplexing
Required
bandwidthPeak cell rate oftraffic type 1
Peak cell rate oftraffic type 2
Peak cell rate oftraffic type 3
Statistical Multiplexing Gain
8/11/2019 ATM Basic v1
7/597 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM interfaces in 3G network
UNI User Network InterfaceNNI Network Node Interface
PSTNMGW MSCBSUE
A BIu-CSIubUu
UNI NNI
IP networkGGSN
Iu-PS
NNI
RNC
SGSN
RNCBS
BS
Iur
NNI
UNI
UNI
ATM is employed
Gn Gi
8/11/2019 ATM Basic v1
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8 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Essential for 3G
ATM Cell
ATM Virtual Path (VP) and Virtual Channel(VC)
ATM Adaptation Layer (AAL) (AAL2 andAAL5)
ATM Layer Service Class (CBR,UBR)
ATM Cross Connect
Inverse Multiplexing for ATM (IMA)
ATM over PDH and SDHFractional E1 and Circuit Emulation Service(CES)
8/11/2019 ATM Basic v1
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9 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM cell
Header contains routing and error control information
Payload carries the actual user information, either voice, data orvideo
Header5 bytes
Payload48 bytes
53 bytes
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10 Nokia Siemens Networks Presentation / Author / Date
For internal use
GFC Generic Flow ControlVPI Virtual Path IdentifierVCI Virtual Channel Identifier
PT Payload TypeCLP Cell Loss PriorityHEC Header Error Control
User Network Interface (UNI) Network Node Interface (NNI)
VCI
GFC VPI
VPI
VCI
VCI PT CLP
HEC
123457 68
VCI
VPI
VPI
VCI
VCI PT CLP
HEC
123457 68
Payload Payload
Header(5 bytes)
Payload(48 bytes)
Provides local functions,such as identifying multiplestations that share a singleATM interface
The 1st bit - indicates whether thecell contains user data or controldataThe 2nd bit - indicates congestion
Indicates two levels ofpriority for ATM cells,CLP=1 should bediscarded in preference tocells with the CLP=0
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11 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM cell header
GFC provides local functions.VPI indicates the virtual path over which the cell should berouted.
VCI identifies a virtual channel over which the cell is totravel.
PT discriminates between a cell carrying managementinformation or one, which is carrying user information.
CLP indicates two levels of priority for ATM cells.
HEC checks for an error and corrects the contents of theheader by using a CRC algorithm.
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12 Nokia Siemens Networks Presentation / Author / Date
For internal use
VCI / VPI FieldFunctions
Switching Identifiers Routing
Multiplexing
The concept of virtual channels and virtual paths
Identifiers
VCI identifies a Virtual Channel
Connection VPI identifies a Virtual Path Connection
Transmission Path could be PDH orSDH
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13 Nokia Siemens Networks Presentation / Author / Date
For internal use
Adaptation
Layer
ATM
Layer
Physical
Layer
Conversion to
ATM Data
Types, 48-Byte
Length
Forward Cell
Through
Network
Add 5-Byte
Header
Convert To
Correct
Electrical Or
Optical
Format
Voice
Cell
Data
Cell
Video
Cell
Services
A
ATM Cell Creation
8/11/2019 ATM Basic v1
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14 Nokia Siemens Networks Presentation / Author / Date
For internal use
Hierarchy
Virtual channel connection
AAL2 connection
Virtual path connection
Transmission path
AAL2 link
Virtual channel link
Virtual path link
Physical link
VPCTP
VCCTPVCLTP
VPLTP VPLTP VPLTP VPLTPVPCTP
VCLTPVCLTPVCLTPVCCTP
Transmission path
VP
VCs
CIDs
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15 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM in VP and VC
48 bytes
5 bytes
HEADER PAYLOAD
ATM cell (53 bytes)
Transmission
path
Virtual
Path
(VP)
Virtual
Channel
(VC)
ATM Cell
ATM Layer
HEADER
PAYLOAD
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16 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Adaptation Layer
Typical
Use
FixedConnection
Video&
Audio
FrameRelay
IPServices
AALAAL1 AAL2 AAL3/4 AAL5
Connection OrientedConnection oriented or
connectionless
Synchronised Not Synchronised
Constant VariableBit Rate
Source & Dest.
Connection
ATM Layer
Physical Layer
A B C D
ATM Service Classes
PBX
Video Voice DataAA
L
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17 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM layer functions
Convergence Sublayer (CS)
PayloadPayload HeaderHeader
48 bytes5 bytes
User data
AAL
Segmentation and ReassemblySublayer (SAR)
ATM Layer
Transmission Convergence(TC)
48 bytes
Physical Medium Dependent(PMD)
SDH
O/H
PayloadHeader
Scramble frame and adaptsthe signals to the optical orelectrical transmissionmedium
STM-1 Frame
PhysicalLayer
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18 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Adaptation Layer 2 (AAL2)
One AAL2 cell flow consists of variable length "mini-cells" that are concatenated as acontinuous stream into the 48-byte payload areas of ATM-cells
The "mini-cells" are officially called CPS-packets (Common Part Sublayer), & aredivided into packet header (PH) and packet payload (PP) parts
Mini-cells have a "mini-header" (CPS-PH) to identify the channel and length of themini-cell
Mini-cell payload size can be anything from 1 to 45 bytes
Channels can be multiplexed in any order desired, mini-cells can cross ATM-cellboundaries, cells can be padded
All AAL2 ATM-cells begin with a start field which indicates the offset to 1st completemini-cell within the ATM-cell
AAL2 ATM-cell flow
Cell payloadCell header
Channel 3 flow
Start field CPS-PH CPS-PP
Channel 1 flow
Channel 2 flow
Offset to next CPS-PDU
Zero padding
Crossing cellboundary
AAL2 (ATM Adaptation Layer 2)
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19 Nokia Siemens Networks Presentation / Author / Date
For internal use
AAL2 (ATM Adaptation Layer 2)
String of AAL2 Packet Data Units String of AAL2 Packet Data Units
1 2 3 4 5 6
AAL2header
ATM CELLHEADER
ATM CELLHEADER
HEADER= 5 BYTES
PAYLOAD= 48 BYTES
1 2 3 4 4 5 6
ATM cell
OFFSET FIELD, 1 byte (indicates where the next AAL2 PDU starts)
AAL2 PACKET, fixed header, variable length payload (max. 48 bytes)
ATM CELL, 5-byte header + 48-byte payload
PADDING
8/11/2019 ATM Basic v1
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20 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Adaptation Layer 5 (AAL5)
AAL5 ATM Adaptation layer is designed to carry fast streams of longer packets over
ATM as simply as possibleAAL5 doesn't provide any multiplexing itself, it is assumed that the packets carried
identify themselves to higher protocol layers (like TCP/IP)
AAL5 is also known as SEAL (Simple Efficient Adaptation Layer)
Packets are simply segmented into 48-byte fragments of ATM-cell payloads, the lastcell is padded and terminated with AAL5 trailer of 8 bytes
AAL5 trailer indicates packet length & has 32-bit CRC
Packets can be up to 64 Kbytes and are aligned to cell boundaries
The last cell of a packet is indicated by setting the PT[0] bit in cell header
Packet #1
cell #1 cell #2
Cell payload
Cell header
Packet #2
cell #3 cell #4
Zero padding
AAL5 packettrailer
UU
CPI
CRC-32
length
Crossing cellboundary
AAL5 packettrailer
Zero padding
AAL5 (ATM Adaptation Layer 5)
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21 Nokia Siemens Networks Presentation / Author / Date
For internal use
AAL5 (ATM Adaptation Layer 5)
PADDING FIELD, variable length to fill the 48-byte ATM cell
AAL5 PACKET, fixed trailer, variable length payload (max. 64 Kbytes)
ATM CELL, 5-byte header + 48-byte payload
AAL5 Packet Data Unit
USER DATA - Variable length 1 - 65 535 bytes
PAYLOAD= N x 48 BYTES
AAL5trailer
ATM cell 1 ATM cell 2... ..ATM cell n
AAL5 Packet Data Unit
USER DATA - Variable length 1 - 65 535 bytes
ATM L S i Cl
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22 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Layer Service Classes
CBR (Constant Bit Rate)
VBR (Variable Bit Rate)
ABR (Available Bit Rate)
UBR (Unspecified Bit Rate)
Time
Bandwidth
Time
Bandwidth
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23 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM capacity of an E1 frame
Number of bytes with ATM payload is 30 in a frame
Frame repetition rate is 1/125 us.30 bytes/125 us = 240 000 bytes/s
One ATM cell has 53 bytes/cell .
The ATM traffic capacity in a 2 Mbps frame is
240000/53 = 4528 cps or
30 ts * 8 bit * 8000 = 1920000 bits/s = 1920 kbps
ATM over
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24 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM cell mapping into PDH 2048 kbps
PDH frame structure for 2048 kbps is describedin ITU-T Recommendation G.704
ATM cell is mapped intobits 9 to 128 and bits 137 to 256
(i.e. time slots 1 to 15 and time slots 17 to 31)Time slots 0 and 16 are not used for ATM cell
Bit 1 Bit 8
Bit 9 Bit
Bit 121 Bit 12
Bit 129 Bit 13
Bit 137 Bit 14
Bit 249 Bit 25
TS 1
TS 0
TS 30
TS 31
ATM overPDH
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ATM over SDH
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26 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM over SDH
VC-4
OVERHEAD
STM-1 (155,52 Mbps) can fit 44.15 cells per frame-> 353 207 cells per second.
VP1
VP2
VP3
.
.
.
ATM Capacity in STM 1 VC 4 Frame
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27 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Capacity in STM-1 VC-4 Frame
Payload of the STM-1 frame can accommodate 1 Virtual ContainerLevel-4 (VC-4)
Total ATM capacity in a SDH frame:
Payload per virtual container: 260x9 = 2340 bytes
Frame repetition rate is 125 us.
2340 bytes/125 us = 18 720 000 bytes/s One ATM cell has 53 bytes/cell .
The ATM traffic capacity in a SDH frame is: 18 720 000 bytes/s/53 bytes = 353 207 cps
In case STM-0 is used (3x VC3 within STM-1) 114113 cps areavailable per logical interface
ATM Cross Connection
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28 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM Cross Connection
From the origin to the termination of a Virtual Channel Trail there can be multipleintermediate Nodes where ATM Cross Connections might occur
Aggregation close to the BTS saves in transmission costs However in many networks there is only one switch between the BTS and RNC
Traffic is collected from different origins to same destination
Statistical multiplexing gain can be achieved
RNC
STM1
BTS
E1
BTS
E1
BTS
E1
BTS
E1BTS
E1
VP and VC Cross Connections
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29 Nokia Siemens Networks Presentation / Author / Date
For internal use
VP and VC Cross Connections
ATM cross connections can be performed at VP or VC level VP level switching is preferred in some cases as it makes management and
configurations easier The physical link is terminated at any intermediate Node
Virtual Paths can be cross connected to any Physical Interface
Virtual Channels can be cross connected to any Virtual Path
Which layer is terminated depends on the Cross Connection Level
Cross Connections are carried out according to a Cross Connection Table
VC Cross
Connection
VP Cross
Connection
VCI 21VCI 22
VCI 21
VCI 22
VPI 1
VPI 4
VPI 1VPI2
VPI3
VCI 21
VCI 22
VCI 24
VCI 23
ATM Cross Connect
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30 Nokia Siemens Networks Presentation / Author / Date
For internal use
VPI 1
VPI 2
VPI 3
VPI 4
VPI 5
VPI 6
VCI 1VCI 2
VCI 1
VCI 2
VCI 3
VCI 4
VCI 3
VCI 4
VCI 5
VCI 6
VCI 5
VCI 6
Virtual Path Switching
VPI 1
VPI 2
VCI 1
VCI 2
VCI 1VCI 2
VPI 1
VPI 4
VCI 4
VCI 5
VCI 6
VCI 3
VPI 5Port 1
Port 2
Port 3
Virtual Channel Switching
VPI and VCI values
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31 Nokia Siemens Networks Presentation / Author / Date
For internal use
VPI and VCI values
VPI re-use
One VPI value can be used once in the same ATM interface. Can be re-used in another ATMinterface
VCI re-use
One VCI value can be used only once within the same VP, but can be re-used in another VPVP Cross Connection:
VPIs will be re-assigned on the other interface, but could have previous value if available.
VCIs remain the sameVC Cross Connection
The VP will be terminated The VCI will be re-assigned on the VP but could have previous value if available.
ATMUNI
ATMNNI
ATMNNI
ATMUNI
VC-levelXCON
VP-levelXCON
VC-levelXCON
VPI/VCI is modified atconnection points
VPI/VCI is assigned atendpoints
VPI = 37VCI = 41
VPI = 7VCI = 65
VPI = 12VCI = 41
VPI = 57VCI = 65
ATM cross-connect (AXC)
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32 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM cross-connect (AXC)
VC2 / VP2
VC1 / VP1
RNC
ATMswitch
VC1 / VP1
BTS 1
AXC
VC3 / VP3VC3, VC4 / VP4
VC3, VC4, VC5, VC6 / VP7VC5 / VP5
VC6 / VP6
VC1/VP1 THROUGH-CONNECTED IN AXC2
VC/VP CROSS-
CONNECTION TABLEVC3/VP4 VC3/VP 7VC4/VP4 VC4/VP 7VC5/VP5 VC5/VP 7VC6/VP6 VC6/VP 7
AXC / ATM switch
BTS 2
AXC
BTS 3
AXC
BTS 4
AXC
BTS 5
AXC
BTS 6
AXC
StandaloneAXC
ATM resource management Iub
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33 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATM resource management Iub
P
hyTTP
ATMlo
gicalinterface
VP
Ltp
VPLtp
VC
Ltp
ATMlo
gicalinterface
VP
Ltp
VPLtp,
O&M traffic (UBR)
Signalling and user traffic (CBR)
VC
Ltp
VCLtp
VCLtp
VCL
tp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
Common NBAP link (C-NBAP)
Dedicated NBAP link (D-NBAP)
Dedicated NBAP link (D-NBAP)
AAL2 signalling link (AAL2SL)
AAL2 signalling link (AAL2SL)
AAL2 user plane link (AAL2UD)
AAL2 user plane link (AAL2UD)
AAL2 user plane link (AAL2UD)
VCLtp
VPLtp
AAL2 user plane link (AAL2UD)
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
RNC
WAM
WAM
P
hyTTP
O&M / Usage IPOAM
Inverse Multiplexing for ATM (IMA)
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34 Nokia Siemens Networks Presentation / Author / Date
For internal use
Problem ?:More bandwidth than 2 Mbit/s is needed, but
only T1/E1 services are offered by the carrier
PBXPBX
ATM
E1 based
Inverse Multiplexing for ATM (IMA)
PBX PBX
ATM
E1 based
Multiple T1/E1s are bundled for more bandwidth
Solution IMA
Concept of IMA
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35 Nokia Siemens Networks Presentation / Author / Date
For internal use
Tx direction:cells distributed across links in round robin seque
Rx direction:cells recombined into single ATM stream
Physical Link #0
Single ATM Cell Streamfrom ATM Layer
IMA Virtual Link
IMA Group
PHY
PHY
PHYPhysical Link #1
Physical Link #2
IMA Group
PHY
PHY
PHY
Original ATM CellStream to ATM Layer
p
Low bit rate transmission lines can be combined into a group thatseen as a single virtual link by ATMIMA sublayer is part of the physical layer.
It is located between the traditional Transmission Convergence sublayer andthe ATM layer.
Inverse multiplexing for ATM
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36 Nokia Siemens Networks Presentation / Author / Date
For internal use
Inverse multiplexing for ATM
ATM Layer
Physical Medium Sublayer
TransmissionConvergenceSublayer (TC)Physical Layer TC
IMA
Iub IMA max 8 E1Iur IMA max 16 E1All E1 in IMA have to belong to same NIP or IFUOnly one ATM interface/ IMA group
NIP1 can have up to 16 ATM Interfaces
IMA frame - ICP cell, Filler cell
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37 Nokia Siemens Networks Presentation / Author / Date
For internal use
ATMATM ICPFiller
Cell0
Cell1
Cell2
Cell3
Cell4
Cell5
Cell6
Cell7
CellM-1
ATM ATM ATM ATMFiller
FillerFiller ICPATM ATM ATMATMATM ATM
An IMA Frame
M consecutive cells transmitted on each link within the IMA group M can be 32, 64, 128 or 256. NSN default: 128
The ICP (IMA Control protocol) cell is sent once per IMA frame on each link witha different offset between different links, to adjust for differential link delays ICP fields contain e.g. link ID, IMA ID, IMA Frame Sequence Number, ICP Cell Offset
If there are no ATM layer cells to be sent the transmit IMA sends Filler cells.
Note: IMA is not saving bandwidth but enables to utilize the available bandwidthmore efficiently and protects from link and interface failure!
IMA failure case
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38 Nokia Siemens Networks Presentation / Author / Date
For internal use
Upon the failure of one or more links or interfaces of an IMA group, the IMAEngine is able to recover and reassign the distribution of ATM cells to the
remaining working PDH links within the IMA group. Only the capacity of this IMA group is reduced but the IMA group remains operational.
The recovery time of the IMA engine upon PDH link failure is 2 s, all existingcalls will be terminated.
Example:
IMA group with 4 E1 links An ATM interface with a VP of 17000 cps is assigned to that group
Note: IMA group with 4 E1s provides a capacity of 17961 cps
Minimum number of links is set to 2
In case 1 or 2 E1s drop out the IMA group continuous operating after restart with alimited bandwidth even if the logical interface cannot provide anymore the assigned
VP capacity
Transmission (2G/3G)
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39 Nokia Siemens Networks Presentation / Author / Date
For internal use
Transmission (2G/3G)
TDM Channel based allocation (16kbit/s, 64kbit/s etc)
ATM
Cell based allocation (1 ATM Cell =53 bytes, 424 bits (vs. 256bits in E1 (32 TS)))
1 ATM cell requires more than one E1 frame
Usable capacity for ATM in E1 is 1920kbit/s (30x64kbit/s) In case fractional E1 is used -> TS16 available
Transmission (2G/3G)
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40 Nokia Siemens Networks Presentation / Author / Date
For internal use
Transmission (2G/3G)
234
567891011121314
1516171819202122232425262728293031
10 LINK MANAGEMENT
TCH 1TCH 5TCH 1TCH 5
TCH 1TCH 5TCH 1TCH 5TCH 1TCH 5TCH 1TCH 5
TCH 2TCH 6TCH 2TCH 6
TCH 2TCH 6TCH 2TCH 6TCH 2TCH 6TCH 2TCH 6
TCH 3TCH 7TCH 3TCH 7
TCH 3TCH 7TCH 3TCH 7TCH 3TCH 7TCH 3TCH 7
TCH 4TCH 8TCH 4TCH 8
TCH 4TCH 8TCH 4TCH 8TCH 4TCH 8TCH 4TCH 8
TRX#1
TRX#2
TRX#3TRX#4
TRX#5
TRX#6
Sector#1
Sector#2
Sector#3
ATMATM traffic768 kbit/s
TRXSIG 1 TRXSIG 2 TRXSIG 3 TRXSIG 4TRXSIG 5 TRXSIG 6 OMUSIG TRXSIG1-
6&OMUSIGAvailable for TDM traffic
Available for TDM traffic
Transmission (2G/3G; Fractional E1)
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41 Nokia Siemens Networks Presentation / Author / Date
For internal use
Transmission (2G/3G; Fractional E1)
RNC
BSC
ET
Node B AXC
IFUA
ATMtraffic
TRS EQ
TRS IF NIU
E1
2G BTSTRUx
TDMtraffic
Fractional E1(TDM+ATM)
TDM X-connect
ATMSWITCH
ATM over E1
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42 Nokia Siemens Networks Presentation / Author / Date
For internal use
Header Payload
0 1 2 16 1817 3115
TS0TS1-15
TS16TS17-31
. . . . ..
0 1 2 16 1817 3115
TS0TS1-15
TS16TS17-31
. . . . ..
E1 frameE1 frame
Fractional E1
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43 Nokia Siemens Networks Presentation / Author / Date
For internal use
3G ATM Traffic Sharing GSM 2M Frame
MetroHub
GSM
BTS
WCDMA
BS RNC
BSC
TDM
Fractional E1
Fractional E1
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44 Nokia Siemens Networks Presentation / Author / Date
For internal use
- INFractional E1 some timeslots are not used for ATM traffic(configurable by management), TS0 and TS16 are not allowed by default
- using only three timeslots provides a 192 kbit/s transmission path for ATM- long transmission delays for ATM traffic!
TS0 TS0
fractional E1termination point
fractional E1termination point
3 octets of the ATM cell 3 octets of the ATM cell
53 octets per ATM cell
Circuit Emulation Service (C
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45 Nokia Siemens Networks Presentation / Author / Date
For internal use
GSM Traffic Over ATM
SAXC or
WCDMA
BTS-AXC
GSM
BTS
WCDMA
BS RNC
BSC
ATM
CES
Circuit Emulation Service (C
Circuit Emulation
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46 Nokia Siemens Networks Presentation / Author / Date
For internal use
RNC
BSC
ET
E1 from 2G BTS
ATMSWITCH
Non fractional E1
AXCIFU A
NIU
2G BTSTRX
TRX
TRX
TRX
TRX
TRX
TRUA
D-busLIF1
WSP WSP
3G BTS AXC
...
WSP WSP...
IFU A
IFU EWAM
WAM
CESIWF
Flexbus connection
E1
VCC
VCC
VCC
VPC
AXU
CESIWF
VCC
VCC
VCC
VPC
IFU E
Unstructured Circuit Emulation Service
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47 Nokia Siemens Networks Presentation / Author / Date
For internal use
- Transmitting CES interworking function takes the E1 si and segments that stream into ATM cells- ATM cells are transported via a CBR VCC to the receiving CES
interworking function- receiving CES interworking function recovers E1 signal from the A cell stream- Note: CES works bidirectional
CESInterworking
Function (IWF)
CESInterworking
Function (IWF)
TS0 TS0 TS0 TS0
G.703 frames
Structured Circuit Emulation Service
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48 Nokia Siemens Networks Presentation / Author / Date
For internal use
- Transmitting CES interworking function takes only sometimeslots
from the E1 signal puts these into ATM cells
- ATM cells are transported via a CBR VCC with lower bandwidthcompared tounstructured CES to the receiving CES interworking function
- receiving CES interworking function recovers TS from the ATM cellstream- Note: CES works bidirectional
CESInterworking
Function (IWF)
CESInterworking
Function (IWF)
TS0 TS0 TS0 TS0
TS1-TS3
Protocol Stacks of User Plane for CS/PS services
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49 Nokia Siemens Networks Presentation / Author / Date
For internal use
AAL2
PHY
ATM
PHY
ATM
AAL2
FP
PHY
AAL2
PHY
ATM
LinkLayer
PHY
AAL2
PHY
ATM
WCDMAL1
FP
WCDMAL1
E.g.,Vocoder
PHY
PSTN/N-ISDN
MGW
RNC
BTS
UE
Iu-CS UP
E.g.,
Vocoder
LinkLayer
A/m-lawPCM,UDI,etc.
A/m-lawPCM,UDI,etc.
MSC
RLC-U
MAC
RLC-U
MAC
UE BTS RNC MGW / MSC /SGSN GGSN
IP
AAL5
PHY
UDP
LLC/SNAP
GTP-U
ATMPHY
ATMAAL2
FP
PDCP
UDP
IP
LinkLayer
PHY
GTP
IP
AAL5
PHY
UDP
LLC/SNAP
GTP-U
ATM
UDP
IP
LinkLayer
PHY
GTP
AAL2
PHYATM
WCDMAL1
FPWCDMA
L1
PDCP
E.g.,IPv4, IPv6
PHY
E.g.,IPv4, IPv6
GGSN
3G-SGSNRNC
BTS
UE
RLC-UMAC
RLC-UMAC
Also forNRTservicesAAL2 isused onATM asTransportLayer
Iu-CS UP
Iub
IuUu
Quality of Service
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To guarantee the required QoS, there is a method defined to describe connectionsbehavior
Service category classifies connections as CBR,UBR or UBR+
Traffic parameters define mainly the bandwidthrequirements e.g. PCR / MCR
QoS parameters define finally the QoS of the
Connection such as delay, cell loss etc.
Service Classes
Traffic Parameters
QoS Parameters
QoS Class
The combination of the Traffic Class and
the set of Traffic and QoS parametersconstitute the Connection TrafficDescriptorof an ATM connection
ATM service categories - CBR
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CBRConstant Bit Rate
Used for constant (maximum) bandwidth
services For the connections that request a fixed
(static) bandwidth, that is continuouslyavailable during the connection lifetime
Is intended to support real-time applicationsrequiring tightly constrained delay variation
The applications are e.g. video, audio, circuitemulation, but use of CBR does not restrictedto those applications
PCR is guaranteed
Used for signaling traffic (CNBAP, DNBAPand AAL2SIG)
Used for user plane VCCs All user plane VCCs CBR in RNC until RAS06
Time
Bandwidth
ATM service categories - UBR
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UBRUnspecified Bit Rate
Is intended for non-real-time applications,
i.e., those not requiring tightly constraineddelay and delay variation.
Examples of applications are traditionalcomputer communication applications,such as file transfer and email
Service does not specify traffic relatedguarantees
Sources are expected to transmit non-continuous bursts of cells
PCR is not guaranteed and
Traditionally DCN and Iu-PS connectionshave been UBR
Time
Bandwidth
?
ATM service categoriesUBR+
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UBR+Unspecified Bit Rate + Is intended for non-real-time applications,
i.e., those not requiring tightly constraineddelay and delay variation.
Examples of applications are traditionalcomputer communication applications,such as file transfer and email
Specified with PCR and MDCR
MDCR is guaranteed and traffic can be
transmitted up to PCR (in RNC) Picture is indicating that even though the
MDCR is reserved for the traffic, the trafficcan reach up to the PCR, if there is freecapacity to be used e.g. in the VPC orBundle
Time
Bandwidth
PCR
MDCR
Note! UBR+ has also proprietaryUBRshare parameter that is used to
share excess capacity between different
UBR+ VCC in the line card.
Traffic and QoS Parameters
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Traffic parameters describe traffic in terms of: PCR - Peak Cell Rate
Maximum bandwidth in any situation MDCR - Minimum Desired Cell Rate
Parameter defines the guaranteed cell rate
QoS Parameter: CDVT - Cell Delay Variation Tolerance
This parameter is set according to network element requirements (details follow!) CLR - Cell Loss Ratio:
Describes the ratio of lost cells to transmitted cells
The CLR parameter is the value that the network agrees to offer as an objective overthe lifetime of the connection
If value will be exceeded an alarm will be raised or possibly further action will be
triggered depending on parameter settings Usual values between 10-3to 10-9
Traffic Management
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Traffic management is needed in order to comply to the QoS requirements
QoS is guaranteed as long as the connection is compliant with the Traffic
contract The traffic offered to the network can be variable and therefore end-to end
participation of network elements is required
Picture: Traffic management functions with in ATM node are distributed among differentelements
Policing
CAC
Interface
Control
module
Switch fabric
BufferingCongestion control
Queuing
Traffic priorities
Shaping
Buffering
Interface
IngressCells in
EgressCells in
Traffic Contract
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Definition of a Compliant Connection
QoS class
Traffic Descriptor
Cell Delay Tolerance
Cell Loss Ratio
Peak Cell Rate
Service Category
A
Traffic contract is negotiated during connection establishment
Its an agreement between a user and a network, where the network guarantees
a specific QoS if the user's cell flow conforms to a negotiated set of trafficparameters
A traffic contract can be also a written contract between an Operator and e.g. abackbone / Leased Line provider.
Traffic contract of includes:
Definition of a Compliant Connection
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QoS is guaranteed as long as the connection is compliant with the traffic contract
Committed to provide the agreed QoS to all cells conforming the traffic contract,
the network needs to police the traffic to detect non-conforming cells Network takes appropriate actions to prevent non-conforming cells from affecting
the QoS of the conforming cells of the other connections
The network could drop cells
Conformance test performed on the traffic stream, defined in the trafficdescription
CBR.1 for CBR (only available for CBR)
UBR.1 for UBR (default), cell will be discarded if non-conformant
UBR.2 for UBR, cell will be tagged (CLP bit set to 1) and forwarded
If conformance definition is UBR.1 then packets violating the traffic contract will bediscarded.
For UBR.2 non-compliant cells will be first tagged (CLP) and then discarded whenrecognized again as non-compliant.
CDVTCell Delay Variation Tolerance
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In this example we assume only 4 VCCs with a low capacity,mapped into an interface of a little higher capacity.
Imagine a SDH-interface with a 23 times higher capacity, wherehundreds of VCCs are mapped in.
Line rate 15kcps = 1 cell every 67s
125s white CV-CDVT = 500s
8000 cps = 400s = 500s = 333s
4000 cps
2000 cps
= 267s = 67s
1000 cps
blue CV-CDVT = 1000s
250 s
500 s
1000 s
XCON
CDVT - Cell Delay Variation Tolerance
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Time budget, how much earlier than expected ATM cells are allowed to arrive
Normally, ATM cells are expected every 1/PCR.
If an ATM cell arrives earlier than expected, the next ATM cell is expected laterthan 1/PCR in order to compensate.
Typical value of CDVT = 1/PCR.
Example:
Line rate = 5000 cell/s1 ATM cell takes 200 s
VCC PCR = 2000 cell/s1 redATM cell per 500s.
CDVT = 1/PCR = 1/2000 s = 500 s.
expected arrival time
actual on or after expected arrival time.
actual prior to expected arrival time,if > CDVT, discard cell.
Bits are received at time ...
400 01200 80016002000t [s]
= 0 s, OK = -100 s
OK
= -300 s, OK
= -600 sNOK
Tx Rx